1. Field of the Invention
The present invention relates to power window apparatuses, and more specifically, to a power window apparatus which allows a door window to be opened by an operation of a window lowering switch if a car drops into water from some reason.
2. Description of the Related Art
If a car accidentally drops into water, electrical insulation between the contacts of a window raising switch and between those of a window lowering switch is unlikely to be maintained in a power window apparatus used for the car. Although each contact of the window raising switch and the window lowering switch is open, actually they are electrically connected. Therefore, even if the window lowering switch is operated, the lowering operation of the window, namely, an opening operation of the window cannot be performed.
FIG. 5 is a circuit configuration of a main part of such a conventional power window apparatus.
As shown in FIG. 5, the power window apparatus is formed of a window raising switch 21, a window raising relay 22 and its contacts 22.sub.1, a window lower switch 23, a window lowering relay 24 and its contacts 24.sub.1, an automatic raising switch 25, an automatic lowering switch 26, a window opening and closing motor 27, a control integrated circuit (IC) 28, and a car power source (battery) 29.
Between the car power source 29 and the ground, the window raising switch 21 and the window raising relay 22 are connected in series, and the window lowering switch 23 and the window lowering relay 24 are also connected in series. A connection point "a" between the window raising switch 21 and the window raising relay 22 is connected to a pin (1) of the control integrated circuit 28. A connection point "b" between the window lowering switch 23 and the window lowering relay 24 is connected to a pin (2) of the control integrated circuit 28. The automatic raising switch 25 is connected between the connection point "a" and a pin (3) of the control integrated circuit 28. The automatic lowering switch 26 is connected between the connection point "b" and the pin (3) of the of the control integrated circuit 28. Among the contacts 22.sub.1 of the window raising relay 22; a movable contact is connected to one end of the window opening and closing motor 27, one fixed contact is connected to the car power source 29, and the other fixed contact is connected to the ground. Among the contacts 24.sub.1 of the window lowering relay 24, a movable contact is connected to the other end of the window opening and closing motor 27, one fixed contact is connected to the car power source 29, and the other fixed contact is connected to the ground. A pin (4) of the control integrated circuit 28 is connected to the window raising relay 24, and a pin (5) is connected to the window lowering relay 24, and a pin (6) is connected to the car power source 29.
The power window apparatus configured as described above will roughly operate in the following way.
When a driver of the car operates the window raising switch 21, its contacts are closed and the car power source 29 drives the window raising relay 22. The contacts 22.sub.1 of the window raising relay 22 are switched on, the window opening and closing motor 27 rotates in one direction, and thereby the window moves in the raising direction (closing direction). When the driver stops operating the window raising switch 21, the contacts become open and driving of the window raising relay 22 is stopped. Therefore, the window opening and closing motor 27 also stops rotaling and raising of the window stops. When the driver operates the window lowering switch 23, its contacts are closed and the power source 29 drives the window lowering relay 24. The contacts 24.sub.1 of the window lowering relay 24 are switched on, the window opening and closing motor 27 rotates in the other direction, and hereby the window moves in the lowering direction (opening direction). When the driver stops operating the window lowering switch 23, the contacts become open and driving of the window lowering relay 24 is stopped. Therefore, the window opening and closing motor 27 also stops rotating and lowering of the window stops.
When the driver operates the automatic raising switch 25, its contacts are closed, the window raising switch 21 is operated at the same time, and its contacts also become closed. Since the contacts of the window raising switch 21 are closed, the car power source 29 drives the window raising relay 22. In the same way as when the window raising switch 21 is operated as described above, the window opening and closing motor 27 rotates in one direction, and thereby the window moves in the raising direction (closing direction). Since the contacts of the window raising switch 21. are closed and those of the automatic raising switch 25 are closed, the voltage obtained at the connection point "a" is supplied to the pins (1) and (3) of the control integrated circuit 28. In response to the supply of voltage, the voltage of the car power source 29 is latched and output from the pin (4) of the control integrated circuit 28, and sent to the window raising relay 22. Therefore, even if the operation of the automatic raising switch 25 is stopped, its contacts become open, the operation of the window raising switch 21 is stopped at the same time, and its contacts become open. Since the voltage output from the pin (4) has been latched, the window raising relay 22 continues being driven, the window opening and closing motor 27 rotates in one direction, and thereby the window continues moving in the raising direction (closing direction). The window continues moving in the raising direction (closing direction) until the window is fully closed.
In the same way, when the driver operates the automatic lowering switch 26, its contacts are closed, the window lowering switch 23 is operated at the same time, and its contacts also become closed. In the same way as when the window lowering switch 23 is operated as described above, the window opening and closing motor 27 rotates in the other direction, and thereby the window moves in the lowering direction (opening direction). Since the contacts of the window lowering switch 23 are closed and those of the automatic lowering switch 26 are closed, the voltage obtained at the connection point "b" is supplied to the pins (2) and (3) of the control integrated circuit 28. In response to the supply of this voltage, the voltage of the car power source 29 is latched and output from the pin (5) of the (control integrated circuit 28, and sent to the window lowering relay 24. Therefore, even if the operation of the automatic lowering switch 26 is stopped, its contacts become open, the operation of the window lowering switch 23 is stopped at the same time, and its contacts become open. Since the voltage output from the pin (5) has been latched, the window lowering relay 24 continues being driven, the window opening and closing motor 27 rotates in the other direction, and thereby the window continues moving in the lowering direction (opening direction). The window continues moving in the lowering direction (opening direction) until the window is fully opened.
If the car drops into water for some reason, and the window raising switch 21 and the window lower switch 23 in the conventional power window apparatus are submerged in water, water connects the contacts of each switch as resistors allowing continuity. Although each contact of the window raising switch 21 and the window lowering switch 23 is open, the output of the car power source 29 is applied to the window raising relay 22 and the window lowering relay 24. The window raising relay 22 and the window lowering relay 24 are driven at the same time, or they are half driven at the same time. As a result, their contacts 22.sub.1 and 24.sub.1 are switched at the same time, or the contacts 22.sub.1 and 24.sub.1 cannot switched to either fixed contacts. In this condition, even if the driver operates the window lowering switch 23 to open the window, the window opening and closing motor 27 is not rotated.
As described above, if the car drops into water accidentally and the conventional power window apparatus is submerged in water, the apparatus cannot be operated normally any more.